Design and synthesis of thieno[3,4‐c]pyrrole‐4,6‐dione based conjugated copolymers for organic solar cells

Abstract

A new series of conjugated copolymers (PBDT-TPD, PBDT-Th-TPD, PBDT-TT-TPD) containing donor-acceptor (D − A) structure electron-rich benzo[1,2-b:4,5-b ′ ]dithiophene (BDT) units with branched alkyl thiophene side chains and electron-deficient 5-(2-octyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD) units was designed and synthesized. To tune the optical and electrochemical properties of the copolymers, the conjugation length of the copolymers was extended by introducing -conjugated spacers such as thiophene and thieno[3,2-b]thiophene units. It was observed that PBDT-TPD showed broader absorption spectra in the longer wavelength region and the absorption maximum was red-shifted compared to that of PBDT-Th-TPD, PBDT-TT-TPD. Stokes shifts were calculated to be 52 nm for PBDT-TPD, 153 nm for PBDT-Th-TPD and 146 nm for PBDT-TT-TPD. Further, PBDT-TPD exhibited a deeper highest occupied molecular orbital energy level of −5.53 eV as calculated by cyclic voltammetry. Bulk heterojunction solar cells fabricated using PBDT-TPD as donor material exhibited a power conversion efficiency of 1.92%.

Research progress and application of high efficiency organic solar cells based on benzodithiophene donor materials

“…Subsequently, based on the reported results of PBDTT-ttTPD, Kotturappa et al selected alkyl chain octyl to replace the original substitution in TPD unit and then synthesizing PBDT-TT-TPD (2017) . [140] Regrettably, the shortening of the solubilized alkyl chain decreases the J sc (4.88 mA/cm 2 ) and FF (37.2 mA/cm 2 ) in PBDT-TT-TPD: PC71BM based OSC. Similarly, Xu et al also preparedPBDT-PS-ttTPD (2023) and PBDT-PO-ttTPD (2023) based on the polymer skeleton BDT-TT-TPD-TT.…”

“…Afterward, to further enhancing the electronegative of TT unit, by creating two active sites and introducing the functional group carbonyl, 4H , 6H -5λ 2 -thieno [3, 4-c ] pyrrole-4,6-dione (TPD) unit with a strong electron-withdrawing was successfully constructed. Subsequently, based on the polymer backbone BDT-T-TPD-T, PBDT-TPD (2014) andPBDTT-TPD (2014) were designed by Kim et al [138] ; P1 (2016) , PBDT-Th-TPD (2017) , PBDT-TTV (2018) and PTPD (2020) were prepared by Kranthiraja et al [139] , Kotturappa et al [140] , Kim et al [141] , and Zhao et al [142] in turn; a series of polymer donors TPD-1 (2020) , TPD-2 (2020) , TPD-3 (2020) and TPD-3F (2020) were also synthesized by Liao et al [143] After applying for OSC devices, the introduction of thiophene-based and benzene-based side chains further extend the π-π conjugated plane of polymer donors, thereby these polymer donor: acceptor based OSC achieved a promisingV oc , especially for P1 (2016): PC 71 BM based OSC (0.99 V). Furthermore, based on the main chain of BDT-T-TPD-T, due to the substitution of alkyl-thiophene side chain extend the original π-π conjugated plane of polymer backbone as well as enhance the electron-donating of BDT unit, meanwhile, the introduction of long alkyl chain also optimized the miscibility and blend film morphology of active layer.…”

Wide‐Bandgap Donor–Acceptor Copolymer Based on BDTTz Donor and TPD Acceptor for Polymer Solar Cells Using Fullerene and Nonfullerene Acceptors

“…Among different electron-deficient units, N-alkylthieno[3,4-c] pyrrole-4,6-dione (TPD) unit is one which has numerous advantages such as easy synthesis, high coplanarity, and strong intermolecular/intramolecular interaction properties. [55][56][57][58][59][60][61][62] Moreover, TDP-based copolymers exhibit a deep HOMO energy level, which not only increases the ambient stability but also helps to achieve the high V OC of the PSCs.…”